1. Field of the Invention
The subject invention relates to a system for supplying fuel under pressure to an internal combustion engine in a marine vessel, and, more specifically, addresses the problem of controlling fuel delivery to a fuel injection system in a marine engine.
2. Description of the Prior Art
In fuel supply systems for marine engines, and in particular for so-called in-board and stern drive type engines, it is often challenging to supply an uninterrupted flow of fuel under all operating conditions. The operating environment is frequently very hot, causing the fuel to vaporize if not carefully controlled. And fuel delivery must be compatible with marine engine run cycles which are characterized by long periods of operation at a steady RPM, punctuated by abrupt instances of rapid acceleration or deceleration. Throughout these cycles and conditions, fuel is expected to be delivered to the engine without interruption.
Furthermore, marine applications are often subject to harsh vibrations and jarring. The fuel delivery system must be heartily designed and fortified to prevent fuel leakage even under violent operating conditions. Leaked fuel on a marine vessel can, in extreme instances, result in fire which may require immediate human evacuation regardless of the vessel location or weather conditions.
Thus, meeting the fuel demands of a marine engine under these operating conditions and in consideration of these safety issues can be a challenge. A prior art technique to provide fuel to a marine engine is shown in applicant's own U.S. Pat. No. 6,257,208, the contents of which are hereby incorporated by reference. According to this technique, a high pressure fuel pump delivers a continual supply of fuel to the engine injector system in sufficient quantities to meet engine demands at so-called ‘full throttle’. When the engine fuel demands are less than ‘full throttle’, a return line is employed to return unneeded fuel from the engine injector system to the vapor separator.
This re-circulation technique is currently state-of-the-art. It is believed to be necessary so that hot fuel in the engine injector system can be cooled to a less volatile temperature by re-mixing with liquid fuel in the vapor separator, and where any fuel vapors can be vented and bled out of the system.
One disadvantage of this technique resides in the requirement to design and fabricate the return line and associated fittings with extremely high quality and durable components to avert the possibility of fuel leakage over the foreseeable service interval of the fuel supply system. This increases both the cost of the fuel supply system and the risk of leakage, particularly where operating conditions are harsh and service intervals extend beyond manufacturer recommendations.